You have two waveforms, one each feeding into X and Y of the scope or laser.
Determine the frequency of each waveform.
Determine how many cycles of each waveform you wish drawn on the screen.
Calculate the total time to draw n lines of that many cycles. Take the longer of the two (X and Y).
Is this time shorter than 25ms?
If not adjust your parameters to make the total time shorter than 25ms otherwise your image will start to flicker.